This invention relates to a method utilizing a directed energy beam to selectively deposit material from a gas phase to either join two or more distinct ceramic, metal or composite bodies, to attach a fastener to such a body or to repair such a body.
Previously, solid compositions have been joined together by a wide variety of techniques depending on materials to be joined. For instance, metal pieces can be joined together by several welding techniques. There are many methods of joining ceramics, metals, and composites presently in use. Examples of the techniques presently used include use of low melting temperature glasses as a binder, sometimes coupled through an electric field; liquid phase joining with low temperature brazes; and solid state bonding by either direct application of pressure and temperature to the parts to be joined or through a lower melting temperature material at the joining interface, sometimes resulting in chemical modification at the interface. In many of these approaches the lower melting temperature binding material limits the operating temperature of the bonded part. In addition, the chemical stability at high temperature can be compromised. The approaches which use pressure require fixturing, and are not readily applicable in many complex geometries. In none of these approaches does the bonding material originate as a gas precursor.
Similarly, methods of attaching fasteners to ceramic pieces are also limited. Typically, fasteners are attached by use of various organic-based glues or by bolting the fastener to the piece. Glues, however, may weaken over time, and bolts usually require drilling holes in the ceramic piece which may weaken the piece or require setting of the bolt in the piece while the ceramic piece is cast.
Techniques for joining ceramics have a wide range of difficulties. Examples of these difficulties are: use of dissimilar fastening material can have problems with mismatch in coefficient of thermal expansion inducing stresses; use of lower melting temperature materials as fasteners limits applicability of the total system at higher temperatures; and introduction of stress risers in the ceramic to accommodate fasteners can lead to fracture of the ceramics. The materials used to make the fastener can add a chemical incompatibility.